Reset a variable on a form

I need to reset the value that is stored in a variable. I am using a repeating section to fill out a form. In that repeating section, I store the value selected from a list lookup in a variable. That part works as intended. However, when I add a section, because that variable contains the same value from the previous section I get a conflict when I try to filter subsequent controls based off that value.

For example:

The value stored in the variable from section 1 would be: "Item1"

The value in the variable when added a section would then become: "Item1, Item2"

I need to reset the variable so that instead of storing the above, it would be cleared to just contain the value "Item2"